Authorities charge Army Staff Sgt. Robert Bales with murdering 16 villagers, but they have limited access to evidence and key witnesses won't testify.

KABUL, Afghanistan — Most everyone was asleep when an Afghan guard at a U.S. military camp spottedthe American soldier walking out the southern gate into the quiet chill of thedesert. A general alarm had been sounded by the time he returned and laid his weapon on the ground.

What happened that night, U.S. authorities say, was one of the most horrific massacres of the war in Afghanistan.

Staff Sgt. Robert Bales, a spit-polished and personable veteran of four deployments in Iraq and Afghanistan, is accused of murdering 16 villagers and attempting to kill at least sixothers. Residents near Camp Belambay said he shot and stabbed people as they rose sleepily from their beds, dragged one woman by her hair and leveled his weapon at a shrieking baby's mouth.

"It was a mess of blood, ashes and burnt clothes," said Mohammed Wazir, who returned from out of town with his youngest son later that morning to find the rest of his family — his mother, wife, six other children, brother, sister-in-law and nephew — all dead.

"It took half an hour to identify everyone. All of the bodies were burnt," Wazir said. He was one of severalvillagers who traveled to Kabul, the Afghan capital, recently to recount what happened during the three-hour rampage outside Camp Belambay.

On Monday, the Army's investigation will unfold at Joint Base Lewis-McChord near Seattle in a two-week hearing to determine whether there is sufficient evidence to hold the 3rd Stryker Brigade staff sergeant for a court-martial on charges of premeditated murder, which could carry the death penalty. The hearing will be conducted in part by video link to allow Afghan witnesses to testify from the other side of the world.

The case presents a challenge to Army prosecutors, who must link Bales, 36, to a crime scene and victims even though U.S. forensic investigators weregivenlimited access. Afghan survivors have already expressed little confidence in the military legal system and balked at having some crucial witnesses testify.

"Hang him. That's what I want. Hang him from the neck; let him dangle," Wazir said. "Let him sit in front of us. Let him look in our eyes. And we will look in his eyes."

Theslayings took place in southern Afghanistan in tworemote farming villages, small clusters of mud brick houses surrounded by fields of pomegranates and grapes. Although the U.S. troop buildup has brought a measure of stability to southern cities, it has failed to offer much protection in the countryside.

Villagers live in fear of the Taliban as well asthe Afghan army and U.S. forces, whose skirmishes play out on their narrow, dusty roads. Days before the massacre, villagers said, Americantroops had angrily questioned nearby residents after aroadside bomb blew off the leg of a friend of Bales.

Shortly after Bales' arrest, Defense Secretary Leon E. Panetta said the staff sergeant was believed to have left the special operations camp in the early morning of March 11, fired on several families, returned to the base and "basically turned himself in, told individuals what happened."

Authorities subsequently said they believed Bales made two trips outside the base that night: one to Alkozai, north of Camp Belambay, one to Najiban, about 1 1/2 miles south.

It is unclear how much physical evidence there will be at the hearing. Families almost immediately buried the bodies as dictated by Islamic tradition, making it difficult for medical examiners to positively identify them and match bullet wounds to a weapon.

Prosecutors could face a situation similar to what happened after the 2005 shootings of 24 civilians in Haditha, Iraq. None of the eight Marines charged ever went to jail,in part because of the lack of physical evidence, said Gary Myers, a defense lawyer in that case.

"Bodies could not be examined, crime scenes were not readily available to be viewed," he said. "It's a prosecutorial nightmare when you can't generate the forensic evidence necessary to link the alleged perpetrator to the crime."

Yet the Army doesn't have to definitively prove all 16 deaths to win a conviction, said Eugene Fidell, a former military prosecutor and defense counsel who now teaches military justice at Yale Law School. "Certainly there have been cases … where murder convictions have been obtained where no body was found," he said.

Another question is whether witnesses will be able to identify Bales. Most of those who saw the shooter are dead. The survivors appear to be women — whose male relatives have been reluctant to allow them to testify, even by video — and children.

Two youths whosurvived the massacre described the horror in detail to the Los Angeles Times, but their description of the killer, whom theycalled "the American," remained vague.